Spirochetes are bacteria of major medical importance. Some of the most fundamental aspects related to their biology or mechanisms of pathogenesis are not understood. One of their unique attributes is their rapid motility. A genetic biochemical approach on Leptospira motility has been initiated, and this approach is being extended to the more medically imprtant Treponema. The results have been significant. Motility mutants of Treponema phagedenis were isolated which lacked the periplasmic flagella (PF). Revertants to motility regained the PFs, indicating the importance of the PFs for T. phagendenis mortility. At least two protein species were found to reside together on the PFs. Preliminary results using two dimensional gel electrophoresis and Western blotting indicate that the PFs are actually comprised of at least five proteins. The present grant aims to determine how these proteins are distributed on the PFs by using monoclonal antibodies, immunogold staining, and electron microscopy. The results obtained should yield information on the complex structure of the PFs and the motility of T. phagedenis. In addition, because these PFs antigenically cross react with T. pallidum and the oral treponemes, the results obtained are likely to be relevant to these other spirochetes. The PF genes of T. phagedenis will be cloned into Escherichia coli using specific monoclonal and polyclonal antisera and lambda vector gtll. The cloned genes will be used to determine the number of PF genes, and their DNA sequence. The results should yield information on PF gene structure. In addition, the clones obtained are likely to be useful in probing and analyzing PF genes from other spirochetes. In the course of testing a model of Leptospira motility, tethered cells were found to coordinately change the shape of the cell ends. These results suggest that a signal functions to coordinate the direction of PF rotation. Because the coordination observed is so rapid, the results suggest a nervelike response in these organisms. The present grant aims to better understand this behavior by analyzing cells undergoing a chemotactic response. Both capillary tube and tethered cell assays will be used in the analysis.